aFaculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, WC1E 7HT London, United Kingdom;jMedical Microbiology, Radboud University Medical Centre, 6525 GA Nijmegen, The Netherlands

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Significance

In vector-borne disease systems, there is mounting evidence that vertebrate hosts become more attractive to disease vectors during infection, yet in human malaria, the underlying mechanism has not been studied. We identified compounds, including aldehydes, that are produced in relatively greater amounts in the skin odor of individuals with malaria, thus demonstrating a basis for this phenomenon in the cues used during mosquito host location. By establishing the attractiveness of these compounds to malaria mosquito vectors in laboratory bioassays, we characterize a process by which Plasmodium infection of humans could lead to increased mosquito biting. These compounds may serve as biomarkers of malaria or be used to enhance the efficacy of chemical lures used to trap mosquitoes.

Abstract

Malaria parasites (Plasmodium) can change the attractiveness of their vertebrate hosts to Anopheles vectors, leading to a greater number of vector–host contacts and increased transmission. Indeed, naturally Plasmodium-infected children have been shown to attract more mosquitoes than parasite-free children. Here, we demonstrate Plasmodium-induced increases in the attractiveness of skin odor in Kenyan children and reveal quantitative differences in the production of specific odor components in infected vs. parasite-free individuals. We found the aldehydes heptanal, octanal, and nonanal to be produced in greater amounts by infected individuals and detected by mosquito antennae. In behavioral experiments, we demonstrated that these, and other, Plasmodium-induced aldehydes enhanced the attractiveness of a synthetic odor blend mimicking “healthy” human odor. Heptanal alone increased the attractiveness of “parasite-free” natural human odor. Should the increased production of these aldehydes by Plasmodium-infected humans lead to increased mosquito biting in a natural setting, this would likely affect the transmission of malaria.

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